This invention relates to a control valve which can be installed into a pipeline between two pipeline flanges and comprises a valve duct arranged in the interior of a housing. The mouth of this duct is fashioned as a valve seat curving convexly against the flow direction. A valve body having a sealing surface curved in the same direction and with the same radius as the valve seat is provided for this valve seat. This valve body is arranged to be pivotable about a pivot axis disposed outside of and in parallel to the axis of the cylindrical surface of the valve seat so that, in the closed position, the axes of the cylindrical surfaces of the valve seat and of the valve body are congruent.
In a conventional check valve (French Pat. No. 1,232,779), constituting a valve which opens in case of a pressure gradient positive in the flow direction and closes in case of a negative pressure gradient, the throttle element, provided with a cylindrical surface which curves convexly against the flow direction, is mounted in the housing with a pivot axis lying below the axis of the valve duct and below the axis of the cylindrical surface of the valve seat. The type of structure with a cylindrical surface curving convexly against the flow permits smaller dimensions than the likewise known type of structure wherein the cylindrical surfaces are curved concavely with respect to the flow direction, since in this type of construction the valve body must then be completely pivoted out of the range of the valve duct, so that the housing must have a large dimension in this portion. In the conventional type of structure, however, even the design with convex cylindrical surfaces does not yield favorable dimensions, since the valve housing must have a considerable bulge on the pivoting side of the valve body, although the latter cannot even be opened to such an extent that, in the completely open position, the valve body is no longer immersed in the flow cross section defined by the valve duct. The manufacturing expenses for such a valve are relatively high, expecially since narrow tolerances must be observed if sufficient tightness is to be obtained. Besides, considerable costs are incurred if such a valve must be exchanged against another one, for example after a leak has developed.
The invention contemplates an arrangement which reduces the manufacturing expenses for a control valve which can be installed between two pipe line flanges, and furthermore which lowers the costs for replacement of such a valve. The invention further contemplates a control valve fashioned so that it can be utilized as a low-noise control valve having a sufficient control accuracy over a large range of its throughflow characteristic, determined by the permitted tolerances for linear or equal-percentage characteristic curves. The invention resides in part in that the valve body and the valve duct form a structural unit exchangeably arranged in the housing, for which purpose the valve body is disposed, with its pivot axis, in an extension of the valve duct projected past the valve seat. The manufacturing expenses are reduced with this arrangement, because the housing has only a subordinate importance for the functioning of the valve, so that no narrow (close) tolerances need be maintained in production of the housing. Moreover, the advantage is attained that, in case of repair or the like, only the structural unit formed by the valve body and the valve duct needs to be exchanged, without having to provide a new housing which, in most cases, consists of a very expensive material. The structural units or modules, which are also advantageous for storage purposes, can readily be tested for tightness individually in the manufacturing plant. Also, this construction makes it possible to provide the valve, by exchanging the module, with a different characteristic, without the expenditure being too excessive for this purpose.
In order to be able to keep the module, and thus also the housing dimensions, at a minimum in size, an advantageous embodiment of the invention provides that the pivot axis of the valve body, preferably intersecting the axis of the valve duct, is disposed below the axis of the cylindrical surface of the valve seat -- as seen in the direction of the pivoting motion. This makes it possible to achieve a complete opening, where the pivot axis, in the axial direction, can be located relatively closely with respect to the valve seat, and the valve body, in the fully open position, does not project excessively beyond the cross section of the valve duct freed by the valve body.
In a further embodiment of the invention, it is provided to form, to keep the noise transmitted to the outside at a minimum, the inner surface of the valve body with a curvature, the apex line of which curvature extends in an extension of the valve duct in the fully open valve position. This creates a configuration of the inner surface of the valve duct which is favorable from the viewpoint of flow dynamics, this inner surface being likewise exposed to the flow of the medium in the open position. Thus, the flow cross section is not restricted and the noise generation can be kept at a minimum. In this construction, the inner surface of the valve body, in the open position, constitutes a limiting wall for the flow, covering dead spaces of the housing. For this purpose, it is furthermore advantageous if the valve body, in cross section, as seen in the flow direction has the configuration of an airfoil profile.
In order to further improve the flow conductance, it is advantageous to provide, as an extension of the valve duct, a sleeve extending preferably to the end of the housing and being provided, behind the valve seat in the pivoting zone of the valve body, with a longitudinal slot adapted to the width of the valve body. Thus, the flow is satisfactorily conducted also in the zone behind the valve seat by the sleeve. To establish a simple connection between the module and the housing, this invention further contemplates providing that the valve duct is threadedly inserted, with an external thread, in a threaded bore of an end wall of the housing. This invention further contemplates providing a centering ring extending into a tubular flange and threaded onto the external thread of the valve duct; which centering ring tapers with its projecting zone from the pipe diameter (of a pipe to be connected to the valve) to the diameter of the valve duct. In a further development of the invention, it is particularly advantageous to provide the housing with flanges on its end faces, by means of which the housing is clamped between the pipe flanges within a space defined by clamping bolts. Due to this arrangement, additional mounting means can be dispensed with, since the entire valve is aligned by the centering ring of the valve duct.
In a structurally advantageous embodiment of the invention, the housing consists of a tubular section disposed preferably concentrically with respect to the axis of the valve duct. This tubular section is provided with an end wall at the front and optionally also at the rear. The end walls then form the flanges contacting the pipe flanges and constitute a receiving means for the module made up of the valve duct and the valve body.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.